In January 2022, Microsoft disclosed a critical vulnerability—CVE-2022-22709—that impacted the VP9 Video Extensions for Windows 10 and 11. This was not just a simple bug—it was a remote code execution (RCE) flaw, allowing attackers to run code on your machine with just a specially crafted video file. If you ever thought watching videos was safe, think again.

This post will break down what CVE-2022-22709 is, how it works, the technical details, and how someone could exploit it. Whether you’re a developer, security enthusiast, or just a regular Windows user, this guide will help you understand the risks and what you can do to stay protected.

What Is VP9 Video Extensions?

VP9 is a popular video codec developed by Google. Microsoft’s free VP9 Video Extensions package allows Windows devices to play VP9-encoded videos in apps like the built-in Movies & TV app, Edge browser, and more.

You can find the VP9 Video Extensions in the Microsoft Store here. Importantly, this is a system-wide extension. If you installed it, every app that plays media can use it.

The Vulnerability: CVE-2022-22709 Explainer

CVE-2022-22709 is a remote code execution vulnerability in the VP9 Video Extensions. The underlying issue is a buffer overflow that happens when the extension parses certain malformed VP9 video files.

- Risk: An attacker could make a malicious VP9 video. When you open or preview it in a vulnerable app, the attacker’s code could run on your computer—potentially installing malware, stealing data, or giving control to hackers.
- Attack Vector: Remote—no user interaction beyond opening a file, or merely previewing it (e.g., in Outlook, File Explorer’s preview pane, or Edge).

Vulnerable Component

The flaw is in the vp9dec.dll file that comes with VP9 Video Extensions.

How the Exploit Works

When decoding VP9 video streams, there’s insufficient validation on buffer boundaries—specifically, in the way reference frames and tile group headers are parsed. A malicious VP9 file can cause the code to write data past the end of an allocated buffer (heap buffer overflow).

Here’s a simplified illustration of the vulnerable code (pseudocode)

// Vulnerable code snippet (simplified)
void parse_vp9_tiles(uint8_t *input, size_t len) {
    // ... some parsing logic ...
    uint8_t tile_data[1024]; // fixed buffer

    size_t tile_len = get_tile_length(input);
    // No proper check if tile_len > 1024
    memcpy(tile_data, input + offset, tile_len); // Potential overflow!
}

Real-life exploit: By crafting a VP9 stream that tricks the parser into reading a large tile length, an attacker corrupts memory, potentially hijacking code execution.

Exploit Details Demonstration

Below is a Python PoC (proof-of-concept) to generate a malformed VP9 file. This doesn’t produce a working exploit but shows how an attacker could start:

# PoC: Create a malformed VP9 video file
# Note: Do NOT open this on vulnerable systems!

with open("evil.webm", "wb") as f:
    # Standard WebM/VP9 header
    f.write(b"\x1A\x45\xDF\xA3") # EBML header
    # ... Add minimal video file structure ...
    # Malformed tile group (overlong length)
    f.write(b"\x00" * 100) # Filler
    f.write(b"\xFF" * 2048) # Big tile to trigger overflow

An attacker would embed shellcode or use common ROP-chain tricks instead of padding.

Real-World Attack Scenarios

1. Email attack: Attacker sends you a VP9 video. Previewing it in Outlook or saving it and double-clicking is enough—no need to “run” a program.
2. Drive-by download: Attacker hosts the video on their website. Viewing it with Edge can trigger the flaw.

References & Microsoft Advisory

- Microsoft official advisory
- NVD CVE record
- Google: About VP9 Codec

How to Stay Safe

1. Update your system: Microsoft fixed this with a patch. Run Windows Update to get the latest VP9 Video Extensions version after January 2022.
2. Remove VP9 Video Extensions: If you don’t need it, uninstall via Settings → Apps → Installed Apps → VP9 Video Extensions.

Conclusion

CVE-2022-22709 reminds us that media extensions—often installed and forgotten—can hide critical vulnerabilities. Always update your software. For IT teams, audit what codecs and media extensions are present on your endpoints.

If you found this breakdown helpful, share it with your team or on social media to raise awareness of hidden “file” risks!


*This post is exclusive to the community. Stay safe, and keep your software updated!*

Timeline

Published on: 02/09/2022 17:15:00 UTC
Last modified on: 02/14/2022 21:29:00 UTC